During some surgical procedures, the surgical patient is placed under general anesthesia To administer a general anesthesia, an anesthesiologist or nurse anesthetist continuously administers a general anesthetic, such as isoflurane and/or a muscle relaxant, and manages the patient's respiration. Often, the anesthesiologist or nurse anesthetist inserts an endotracheal tube into the patient's trachea for administering anesthesia. In some cases, a mechanical ventilator pumps oxygen into the patient's lungs and allows expired carbon dioxide to escape.
To ensure that proper ventilation is taking place, the anesthesiologist or nurse anesthetist typically monitors the levels of oxygen saturation in the patient's blood and the expired carbon dioxide. Pulse oximetry is the technique most often used to detect the level of blood oxygenation, and capnography commonly is used to monitor the expired carbon dioxide level. Of the two types of monitors for detecting proper ventilation, the carbon dioxide monitor is far quicker to indicate an interruption of ventilation since oxygen saturation can remain at a normal or near normal level for several minutes after proper ventilation has ceased. On the other hand, ventilation interruption will immediately give rise to a precipitous drop in the carbon dioxide level.
An increasingly popular alternative to general anesthesia is Monitored Anesthesia Care (MAC) with intravenous sedation. MAC differs from general anesthesia in that MAC involves shorter-acting anesthetics, such as propofol or midazalam, which place the patient in a deep state of anesthesia. A ventilator does not assist the patient, rather the patient breathes self-sufficiently, as if sleeping.
Although shorter acting, MAC drugs are effective hypnotics and analgesics. As a result, MAC has been able to be used for increasingly more surgical procedures that formerly had been performed under general anesthesia. This increases the number of surgeries that may be performed on an out-patient basis.
During MAC anesthesia procedures, oxygen commonly is delivered to the patient either through a facial mask or through a nasal cannula. Either of such delivery devices enables the patient to achieve oxygenation. As in the case of general anesthesia, oxygen saturation commonly is measured by pulse oximetry, using an infrared sensor typically attached to the patient's finger, ear or toe. When a mask is used for administering oxygen, the level of expired carbon dioxide can be monitored easily by placing a capnograph sample line inside the mask. When a nasal cannula is used for administering oxygen, one of the two nasal prongs can be connected to the capnograph sample line while the other prong supplies oxygen.
While both the facial mask and the nasal cannula can be highly effective in delivering oxygen and monitoring expired gas, both can be problematic under certain circumstances. For example, a facial mask can interfere with surgical procedures involving the patient's face, thus usually is not used during such procedures. On the other hand, a split nasal cannula can only be used when both nasal passages are clear. When either nasal passage is closed or even partially obstructed, either oxygen delivery or carbon dioxide monitoring is compromised.
During MAC with sedation procedures, a patient may become so sedate that breathing slows or even stops all together. When a respiration failure occurs, for example due to an obstruction or closure of the patient's airway when the patient's tongue falls back in the pharynx, the anesthesiologist or nurse anesthetist must respond quickly to restore respiration. Usually, the anesthesiologist or nurse anesthetist can restore proper breathing by manipulating the patient's jaw or repositioning of the patient's head. However, sometimes the anesthesiologist or nurse anesthetist must install a mechanical “airway” in the patient's pharynx, either through the mouth or nose, to clear the obstruction.
A typical mechanical airway includes a soft rubber tube having a length sufficient to pass any obstruction in the pharynx and to allow normal respiratory gas exchange through the tube. Usually, such airways have an arcuate shape to conform to the shape of the oral/nasal pharynx. Mechanical airways are quite uncomfortable to conscious patients. Thus, absent critical need, mechanical airways typically are used after the patient is sedated.
Some surgical procedures do not require the deep state of anesthesia obtained from a general anesthetic; MAC procedures or local anesthetic with intravenous sedation are adequate. Local anesthesia involves topical application or injection of a numbing agent, or local nerve depressant, that acts within a zone about the anesthetic application site. Intravenous sedation involves the administration of a drug, such as benzodiazepines or a narcotic, which results in the depression of the central nervous system. However, the objective of intravenous sedation is to produce a degree of sedation whereby rational verbal communication to and from the patient is possible. The drugs and techniques used are calculated to render unintended loss of consciousness unlikely. Thus, intravenously sedated patients tend to be semi-conscious, not completely unconscious.
Surgeons who perform facial plastic surgical procedures, and more specifically, facial reconstruction and rhinoplasty, prefer to employ local anesthetic with intravenous sedation. To avoid obscuring, cluttering or obstructing the surgical field, as well as limit patient discomfort, surgeons avoid the use of anesthetizing masks and minimize the size and number cannulae needed for administering sedation. However, available devices typically are received in and/or fully occlude one or both nostrils of a patient, interfering with the surgical field. Other available devices include mechanical airways that cause discomfort to conscious patients, thus are not amenable to intravenous sedation.
What are needed, and not taught or suggested by prior devices and techniques, are: (1) an apparatus for delivering inhalant and monitoring exhaled fluid; (2) a method of making same; and (3) a method of delivering inhalant and monitoring exhaled fluid.